JPS6310033A - Ring rolling method - Google Patents

Abstract

PURPOSE:To prevent generation of a defect of a rolling material, and also, decrease the number of times of re-heating, and to improve the productivity by controlling a rolling reduction speed or a revolving speed of a work roller, so that an outside peripheral surface measuring temperature of a ring-shaped rolling material satisfies a set temperature range. CONSTITUTION:A ring-shaped rolling material 2 is rotated, its outside diameter is measured by a outside diameter measuring instrument 10, and it is rolled by a pair of work rollers 3, 4 which have been placed in the inside peripheral side and the outside peripheral side. In said ring rolling method, a temperature of the outside peripheral surface of said rolling material 2 is measured extending over the whole surface by a temperature measuring instrument 9. This temperature is inputted to a central processor 11, and a rolling reduction speed, and/or a revolving speed of the work roller are controlled through a rolling reduction device 5 of the work roller 3 of the inside peripheral side being a mandrel roller, and with a driving device 7 of the working roller 4 of the outside peripheral side being a king roller, respectively, so that said measured temperature satisfies a temperature range which has been set in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ring rolling method for hot rolling a ring-shaped metal material.

(Prior Art) A ring rolling method is well known in which a pair of work rolls placed on the inner and outer circumferential sides of a ring-shaped rolled material sandwich the rolled material from the inside and outside and roll the rolled material. .

Generally, in hot rolling, temperature control is strictly carried out because if the process is not carried out within a predetermined temperature range, cracks will occur or the crystal structure will change, resulting in defects in the product.

In order to perform this temperature control, it is necessary to measure the temperature distribution over the entire rolled material, but in general rolling, the shape of the rolled material is simple, so the overall temperature distribution can be predicted by measuring partial temperature. It is possible to do so.

Therefore, in general rolling, temperature control is performed by measuring partial temperatures without measuring the entire temperature. Similar temperature control is carried out in ring rolling.
When the rolled material falls outside a predetermined temperature range, rolling is interrupted and reheating is repeated.

In addition, in ring rolling, the processing rate and strain rate change moment by moment depending on the reduction speed and rotation speed of the work rolls, and the wall thickness becomes thinner as the rolling progresses. This decrease in wall thickness promotes an increase in surface area, leading to an increase in the amount of heat dissipation, which causes an increase in deformation resistance due to a decrease in temperature. Therefore, even if the rolled material is within the rolling temperature range, if the rolling conditions (rolling speed, number of revolutions) are constant, the capacity of the rolling mill will reach its limit (maximum rolling load, roll (the maximum current value of the drive motor is reached). In this way, even when the capacity of the rolling mill reaches its limit, rolling is interrupted and reheating is repeated.

(Problems to be solved by the invention) In conventional ring rolling, the rolled material is reheated due to partial temperature control and the capacity of the rolling mill. It was significantly lower.

In particular, titanium and titanium alloys have a narrow rolling temperature range, and therefore require a large number of reheating cycles, resulting in extremely poor productivity.

That is, when ring rolling is performed by heating titanium and titanium alloys, the temperature range is limited due to material properties. Ti
In the case of -6Al-4V, as it is heated, it changes from α+β phase to 9
Transforms into β phase at 85°C. When ring rolling is performed in this β phase, the ductility and toughness of the product after rolling are extremely reduced. On the other hand, when ring rolling is performed at a low temperature of 600° C. or lower, cracks occur and internal defects occur, making it impossible to obtain a sound product.

Furthermore, in the case of ring rolling, the rolls often have a profile shape to produce products with complex surface shapes, so the temperature distribution in the axial direction becomes complex, so it is necessary to predict the temperature distribution analytically in advance. It is extremely difficult to do so. Furthermore, when the rolled material is fed into the machine, the temperature of a part of the material may drop dramatically due to contact with the rolls, and the temperature distribution in the circumferential direction becomes complicated, making it difficult to predict the temperature distribution in advance. Furthermore, depending on the roll shape and material shape, axial thrust force is applied to the material during rolling, and the end surface may experience an extreme temperature rise due to friction with the structure. Predicting the distribution is extremely difficult.

That is, FIG. 5 shows an example of the temperature distribution in the axial direction, and FIG. 6 shows an example of the temperature distribution in the axial direction.
As shown in an example of the temperature distribution in the circumferential direction in the section taken along line A-A in FIG. 5, the temperature distribution is extremely complicated. Fifth
The figure shows the axial direction of two materials taken from the same ingot, forged, ring forged, and heated ring rolled twice in the past according to a predetermined schedule, immediately after the third hot eye rolling. The temperature distribution of 0 should originally show the same temperature distribution for the two materials, but in reality they are different. In particular, the temperature of the Δ mark is rising at the bottom surface, but ○
On the contrary, the mark is descending. In addition, the temperature at the end surface of the rolled material should be lower than that at the center, but the Δ mark indicates that the temperature is lower during rolling.
The temperature rises due to friction with the structure. In this way, if there is excessive frictional heat generation, there is a risk that the crystal structure will partially change. The low temperature area near the center of FIG. 6 is lower than the surrounding area, but this is the area where heat was lost due to the long contact time with the rolls just before rolling.

In this way, in ring rolling, approximately 100
It has a complicated temperature distribution with a difference of 30 to 50 degrees Celsius in the circumferential direction. These phenomena cannot be observed unless the entire temperature is constantly measured, and it is extremely difficult to predict them analytically in advance.

However, with conventional technology, rolling is performed by measuring the temperature locally without measuring the complex temperature distribution in the axial and circumferential directions, which results in defects and overheating that cause the product to lose its commercial value. There was a risk of

Therefore, the present invention measures the temperature of the entire outer surface of the rolled material, stops rolling if even one point deviates from a predetermined temperature range, and changes the rolling conditions to maximize the capacity of the rolling mill. It is an object of the present invention to provide a ring rolling method in which rolling is performed under conditions that allow the ring to be rolled at its full capacity.

(Means for solving the problems) In order to achieve the above object, the present invention takes the following measures. That is, the feature of the present invention is that a pair of work rolls arranged on the inner circumferential side and the outer circumferential side of the ring-shaped rolled material,
In the method of rolling the rolled material, the temperature of the outer peripheral surface of the rolled material is measured over the entire surface, and the measured temperature satisfies a preset temperature range.
The point is to control the rolling speed of the work roll and/or the rotation speed of the work roll.

(Function) The present invention provides a highly productive method that prevents a decrease in temperature or an excessive increase in temperature during ring rolling by controlling rolling conditions, and allows rolling without repeated reheating.

Figure 4 shows a Ti-6Aj-4V ring 600φto
This is an example showing the changes in surface temperature, average temperature, and center temperature when rolling from X 856φ00 to 1700φ00.
The rolling speed (feeding speed) of the work roll is 0.1 mm/s.
There are two types of rolling: EC and 1.0 m/sec.

As seen in this figure, the temperature of the rolled material changes significantly depending on the rolling speed. In particular, when the rolling speed is high, the amount of heat generated during processing increases within the material, and the amount of heat dissipation decreases due to the shortening of the rolling time, making it possible to maintain or increase the temperature. A similar effect can be achieved by changing the number of rotations of the work rolls.

In other words, the temperature of the rolled material is measured over the entire surface during rolling, the optimum temperature range is set according to the material composition, and the feed speed (reduction speed) of the work roll is adjusted to satisfy this range.
And/or by controlling the rotational speed of the work rolls, the temperature of the rolled material can be maintained.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

What is shown in FIG. 1 is a ring rolling mill 1 used in the present invention.
FIG. 2 is a schematic diagram of the rolling mill 1, which has a pair of work rolls 3.4 arranged on the inner and outer circumferential sides of the ring-shaped rolled material 2. Hereinafter, the work roll 3 on the inner circumference side of the rolled material 2 will be referred to as a mandrel roll, and the work roll 4 on the outer circumference side will be referred to as a king roll.

The mandrel roll 3 is freely rotatable and is moved toward and away from the king roll 4 at a predetermined rolling speed fr by a rolling down device 5. This mandrel roll 3 has
A mandrel load meter 6 is provided to measure the rolling load P.

The position of the king roll 4 is fixed, and the king roll 4 is rotated at a predetermined rotation speed N by a drive device 7. This drive device 7 is provided with an ammeter 8 of a king roll motor,
King roll current■ is being measured.

Reference numeral 9 denotes a temperature measuring device, which measures the temperature distribution θ over the entire outer surface of the ring-shaped rolled material 2.

Reference numeral 10 denotes an outer diameter measuring device, which measures the outer diameter of the rolled material 2.

The lowering device 5, load meter 6, drive device 7, ammeter 8, temperature measuring device 9, and outer diameter measuring device 10 are electrically connected to a central processing unit 11.

FIG. 2 is a flowchart showing an embodiment of the invention. In this case, the rotation speed N of the king roll 4 is
The rotation speed of the mandrel roll 3 is controlled to be constant, and the rolling speed (feeding speed) of the mandrel roll 3 is controlled to control the temperature.
It is controlled only by fr.

The symbols in FIG. 2 are as follows.

(Setting conditions): Minimum temperature TL Maximum temperature TH Product outer diameter D.

Initial rotation speed N.

Initial feed rate fr.

King roll current limit I.

Mandrel load limit P.

Feed speed variation amount Δft Sampling interval Δt (set value); Surface temperature θ (Z, r)2: Axial direction,
r: Circumferential King Roll Current ■ Mandrel Load P Outer Diameter D To explain the flowchart of FIG. Next, the ring-shaped rolled material 2 is rolled into a rolling mill as shown in FIG.
is set, and rolling is started according to the set conditions. During rolling, the temperature measurement device 9 measures the axial direction θ of the rolled material 2.
(Z), the temperature in the circumferential direction θ(r) is measured over the entire outer surface, and the outer diameter of the rolled material 2 is measured by the outer diameter measuring device 1o. These measured values are transmitted to the central processing unit 11.

The central processing unit 11 determines whether the measured temperature θ (z, r) is within the minimum set temperature TL and the maximum set temperature T, and if it is within the set value, continues rolling under the same conditions. death,
If even one point falls outside the above setting range, the mandrel roll 3
The rolling speed fr is increased or decreased according to a predetermined feed speed variation amount Δft. That is, when the highest set temperature TH is exceeded, the speed is decelerated, and when the lowest set temperature TL is exceeded, the speed is increased.

Furthermore, the king roll current ■ is measured by the ammeter 8,
In addition, the mandrel load P is measured by the load cell 6, and the central processing unit 11 determines whether or not these values are within the capacity of the rolling mill 1. If it is within the capacity, rolling is continued further and the capacity is increased. When the limit is reached, rolling is stopped.

On the other hand, the number of revolutions of the king roll 4 is controlled so that the period is constant based on the outer diameter measurement value, and rolling is stopped when the outer diameter value reaches the product size Do.

According to the rolling according to the above-mentioned FIG. 2, the reheat rolling, which had previously been divided into three times, could be completed in one time. Further, the temperature distribution immediately after rolling at that time is shown in FIG. 3 together with the temperature distribution obtained by the conventional method. In Figure 3,
The O mark indicates the conventional method, and the 0 mark indicates the embodiment of the present invention.As is clear from this Figure 3, in the embodiment of the present invention, approximately 40
The temperature increased by ~50°C, and good results were obtained in defect investigation after rolling and machining.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and the rotation speed BN of the king roll 4 may be controlled for temperature control, or the rotation speed N of the king roll 4 may be controlled.
and the rolling down speed fr of the mandrel roll 3 may be controlled.

(Effects of the Invention) According to the present invention, since the temperature of the entire outer surface of the rolled material is measured and controlled, defects due to a local temperature rise or fall will not occur, and furthermore, the temperature of the work roll Since the temperature is controlled by the rolling speed and/or the number of revolutions, rolling can be carried out at the maximum capacity of the rolling mill, reducing the number of times of reheating and improving productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a ring rolling mill used in the method of the present invention, FIG. 2 is a flowchart showing an embodiment of the present invention,
Fig. 3 is a graph of temperature distribution showing a comparison between the embodiment of the present invention and the conventional example, Fig. 4 is a graph showing that the temperature of the rolled material changes depending on processing conditions, and Fig. 5 is the rolled material according to the conventional example. FIG. 6 is a temperature distribution graph in the circumferential direction of a rolled material according to a conventional example. 1... Ring rolling mill, 2... Ring-shaped rolled material, 3...
...Work roll (mandrel roll), 4...'7
- Kroll (King Roll), 5... Rolling yt, 6
...Load cell, 7...Drive device, 8...Ammeter, 9
...Temperature measuring device, 10...Outer diameter measuring device, 11...
Central processing unit.

Claims (1)

[Claims] (1) In a method of rolling a ring-shaped rolled material using a pair of work rolls arranged on the inner and outer circumferential sides, the temperature of the outer peripheral surface of the rolled material is measured over the entire surface, and the measured temperature is In order to satisfy the preset temperature range,
A ring rolling method characterized by controlling the rolling speed of a work roll and/or the rotation speed of the work roll.